
0m3
The child process does not start with syscall(SYS_clone3, ...) + CLONE_VM
Hello, everyone.
It is necessary that the calling process and the child process are in the same memory space.
Therefore, I use the CLONE_VM flag.
But the child process does not start.
It looks like something is wrong with the allocation of memory for the stack.
Could you please explain the reason?
#define _DEFAULT_SOURCE /* syscall() */
#define _GNU_SOURCE
#define _FILE_OFFSET_BITS 64 /* getrlimit() */
#include <sched.h> /* CLONE_* constants */
#include <linux/sched.h> /* struct clone_args */
#include <sys/syscall.h> /* SYS_* constants */
#include <unistd.h>
#include <stdint.h> /* uintptr_t */
#include <stdio.h>
#include <stdlib.h>
#include <err.h> /* err() */
#include <string.h>
#include <unistd.h>
#include <sys/resource.h>
#include <sys/mman.h>
#include <signal.h>
void spawn(void)
{
struct rlimit rlim;
struct clone_args cl_args;
__u64 stack_size;
__u64 *stackBot;
__u64 *stackTop;
pid_t pid;
memset(&cl_args, 0, sizeof(cl_args));
if (getrlimit(RLIMIT_STACK, &rlim) == -1) {
err(EXIT_FAILURE, "getrlimit");
}
stack_size = rlim.rlim_cur;
stackBot = (__u64 *)
mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_GROWSDOWN |
MAP_STACK, -1, 0);
if (stackBot == MAP_FAILED) {
err(EXIT_FAILURE, "mmap");
}
stackTop = stackBot + (stack_size / sizeof(__u64));
cl_args.flags = CLONE_FILES | CLONE_IO | CLONE_VM;
cl_args.exit_signal = SIGCHLD;
cl_args.stack = (__u64) (uintptr_t) stackTop;
cl_args.stack_size = stack_size;
pid = syscall(SYS_clone3, &cl_args, sizeof(cl_args));
switch(pid) {
case -1:
munmap(stackBot, stack_size);
err(EXIT_FAILURE, "syscall");
case 0: /* Child */
printf("Hello from child!\n");
munmap(stackBot, stack_size);
break;
default: /* Parent */
printf("Hello from parent!\n");
break;
}
}
int
main(int argc, char *argv[])
{
spawn();
printf("Before last while\n");
while(1) {
}
return EXIT_SUCCESS;
}
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0m3
Hello, everyone.
The solution is here The child process does not start with syscall(SYS_clone3, …) + CLONE_VM.
BR, Denis
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